Spray guns are used to inject polyurethane foam underneath concrete for the purpose of raising the concrete and filling voids in the concrete. Spray guns typically receive a liquid isocyanate, also referred to as an “A” component, and a liquid blend of polyols, also referred to as a “B” component. These two components are mixed in a mix chamber of the spray gun to form the polyurethane foam. The polyurethane foam is then purged with pressurized air from a fluid housing of the spray gun. However, current spray guns are often bulky, require excessive numbers of components, and are difficult to assemble and disassemble. Thus, there is a need for a more versatile spray gun that will reduce downtime, increase productivity, and lower repair costs.